In both dog and man, pH threshold for release of secretin is investigated. The relationship between acid load delivered in the duodenum and release of secretin is being studied. Interaction between cholecystokinin and secretin in physiological dose on pancreatic secretion of bicarbonate and protein will be studied. Secretin is released by sodium oleate with pH greater than 8.5 in dog. It will be determined whether sodium oleate can stimulate release of secretin and pancreatic secretion of bicarbonate in man also. Another agent, 1-phenylpentanol, that is known to stimulate pancreatic secretion of bicarbonate will also be studied if it stimulates pancreatic secretion as well as release of secretin in dog. Thus, it will be known with certainty that secretin can be released by agents other than acid or bile. Secretin as an enterogastrone will be studied in rats also. The presence of secretin-producing cells will be reinvestigated in dog, and the studies will extend further to assess secretin's biological significance. Biosynthesis of secretin in the canine duodenal mucosa is being investigated. The study on release of secretin in patients with digestive disorders such as chronic pancreatitis and Zollinger-Ellison Syndrome will be continued.